As the walls of the cells are necessarily permeable to fluids, in order to allow the glands to secrete, it is not surprising that they should readily allow fluids to pass inwards; and this inward passage would deserve to be called an act of absorption, if the fluids combined with the contents of the glands. Judging from the evidence above given, the secreting glands of many other plants can absorb salts of ammonia, of which they must receive small quantities from the rain. This is the case with two species of Saxifraga, and the glands of one of them apparently absorb matter from captured insects, and certainly from an infusion of raw meat. There is, therefore, nothing anomalous in the Droseraceae having acquired the power of absorption in a much more highly developed degree. It is a far more remarkable problem how the members of this family, and Pinguicula, and, as Dr. Hooker has recently shown, Nepenthes, could all have acquired the power of secreting a fluid which dissolves or digests animal matter. The six genera of the Droseraceae very probably inherited this power from a common progenitor, but this cannot apply to [page 362] Pinguicula or Nepenthes, for these plants are not at all closely related to the Droceraceae. But the difficulty is not nearly so great as it at first appears. Firstly, the juices of many plants contain an acid, and, apparently, any acid serves for digestion. Secondly, as Dr. Hooker has remarked in relation to the present subject in his address at Belfast (1874), and as Sachs repeatedly insists,* the embryos of some plants secrete a fluid which dissolves albuminous substances out of the endosperm; although the endosperm is not actually united with, only in contact with, the embryo. All plants, moreover, have the power of dissolving albuminous or proteid substances, such as protoplasm, chlorophyll, gluten, aleurone, and of carrying them from one part to other parts of their tissues. This must be effected by a solvent, probably consisting of a ferment together with an acid.** Now, in the case of plants which are able to absorb already soluble matter from captured insects, though not capable of true digestion, the solvent just referred to, which must be occasionally present in the glands, would be apt to exude from the glands together with the viscid secretion, inasmuch as endosmose is accompanied by exosmose. If such exudation did ever occur, the solvent would act on the animal matter contained within the captured insects, and this would be an act of true digestion. As it cannot be doubted that this process would be of high service to plants * ‘Traité de Botanique’ 3rd edit. 1874, p. 844. See also for following facts pp. 64, 76, 828, 831.